This invention broadly relates to processing a plurality of small metal articles by immersion in surface treating baths while confined within a tumbling barrel. More particularly, this invention relates to an apparatus for blowing residual solution off confined articles after the barrel is raised from the bath.
Small metal articles, such as screws or washers, are processed in bulk through a series of cleaning, plating or other surface treating baths while within a tumbling barrel. The tumbling barrel comprises a perforated side wall for admitting solution when the barrel is submerged in a bath and for draining solution after the barrel is raised from the bath. After draining, solution clings to article surfaces or is trapped within the mass of articles. This residual solution, referred to as drag-out, wastefully removes chemical agents from the bath, which is particularly costly for expensive plating metals. In addition, drag-out contaminates the next bath, typically a rinse, which must be treated before being reused or discharged from the plant.
For large workpieces that are processed without a tumbling barrel, drag-out is substantially reduced by blowing solution back into the bath with a compressed airstream. However, this technique has not heretofore been satisfactory for tumbling barrels. When directed from outside the barrel, the airstream blows solution from the barrel wall onto the articles. Also, the perforated wall diffuses the airstream so that it is not sufficiently forceful to dislodge the solution. Introducing an air nozzle within the barrel interferes with processing operations and complicates article handling.
Therefore, it is an object of this invention to provide an apparatus for enveloping a perforated barrel in a manner such that residual treating solution may be blown off articles confined therein. The apparatus causes a forceful airstream to flow through the mass of articles and impinge upon their surfaces with sufficient force to dislodge solution therefrom. Thereafter, the airstream carries the solution out the barrel and back into the bath, thereby recovering it for future use and reducing contamination of subsequent baths.
It is a more particular object of this invention to provide a blow-off apparatus adapted to enshroud a tumbling barrel and to form therewith a plenum having a bottom air outlet such that compressed air blown into the plenum flows over confined articles to dislodge residual solution and to carry the solution out and into the bath, thereby reducing drag-out. The apparatus is adapted to accommodate an existing tumbling barrel. It does not require modification of the barrel, for example, to insert an air nozzle, and does not interfere significantly with processing operations.